With rapid development of the Internet technology, information is frequently exchanged, using electronic mail or messages. When electronic messages are exchanged, in many cases, a reply message is created. Often, the reply message refers to a previously transmitted message. When several electronic messages are exchanged during an ongoing communication, many past messages are typically referred to in the current message, resulting in a long electronic message.
Various types of techniques for improving the readability of an electronic message that has become long as a result of many exchanges of electronic messages have been developed. For example, some techniques use an electronic device in which information on the history and summary of exchanges of electronic messages can be clearly grasped by determining the header part and body part of each electronic message and displaying all the body parts together or hiding all the body parts at the same time. However, using these techniques, when electronic messages are exchanged among a plurality of users, it is difficult to determine which of the electronic messages should be referred to. For example, in a case where a specialist who is a third person is requested to return an answer to an electronic message that includes a question, and the answer from the specialist is returned to a questioner, creation of a reply message to the most recent electronic message means creation of a reply message with a destination which is not the original questioner, but the specialist who is a third person.
In this case, the reply message needs to be created with the questioner who first sent the electronic mail, which includes the question, as the destination, referring to the electronic mail. Thus, a problem exists in that, the larger the number of exchanges of electronic messages, the more difficult it is to retrieve an electronic message that is a basis for requesting the third person to return an answer.